Men who undergo a vasectomy may have an increased risk of advanced or lethal prostate cancer, a new observational study suggests.
Researchers tracked nearly 50,000 men over 24 years, and found those who had a vasectomy were about 20 percent more likely to be diagnosed with aggressive or potentially fatal prostate cancer than those who had not had the procedure.
The researchers called this increase "modest," and said more studies of the possible link are needed.
"I don't think we should conclude from this that people shouldn't get vasectomies, because the absolute risk doesn't go up too much," said study researcher Kathy Wilson, an epidemiologist at the Harvard School of Public Health. "But it does show that there is something going on."
Vasectomies remain a common form of male contraception; the Harvard School of Public Health estimates about 15 percent of American men have had a vasectomy in their lifetime. [Birth Control Quiz: Test Your Contraception Knowledge]
Past studies have linked prostate cancer with vasectomies, but no solid associations have been established because of confounding factors in the research, Wilson said. It could be that it only appears that men with vasectomies are more likely to get prostate cancer because these men undergo more PSA screenings to test for the cancer, or medical check-ups.
And in 2002, a comprehensive New Zealand study of 923 cases of prostate cancer found no increase in the risk of cancer for the men who had a vasectomy.
In the new study, the researchers used data from the Health Professionals Follow-Up Study, which tracked a cohort of men from 1986 to 2010. The researchers avoided having PSA testing as a confounding factor by surveying their participants every two years to gain a comprehensive picture of which men were highly screened and how often.
Over the 24 years, 6,023 men in the study, or about 16 men in every 1,000 in the study developed prostate cancer. About one in four of those studied reporting having had a vasectomy.
The results showed the risk of advanced prostate cancer increased by 20 percent for men who underwent a vasectomy, compared with men who hadn't had the procedure. The risk of dying from prostate cancer increased by 19 percent for men who underwent the procedure, the researchers said.
The researchers also noted that among men who had regular PSA screenings, the risk increased even more by about 56 percent among those who had a vasectomy.
More work must be done before any strong links can be drawn between prostate cancer risk and vasectomies, Wilson said. One of the study's limitations is that it's an observational study, so it shows a link, but not a cause-and-effect relationship, between vasectomies and prostate cancer.
"Men get vasectomies in their 30s and 40s, and prostate cancer when they're 70, and so I feel like it's a very personal choice to decide about family planning when you're young and balancing that with cancer risk much later on," she said.
Wilson said that men should talk to their doctors about regular PSA screening as they age.
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